Process for optimizing a half-tone reproduction on a photoconductor of electrophotographic printers and copiers

Abstract

A printer or copier optimizes half tone printing by a method including printing a raster toner mark and scanning the raster toner mark to determine if it is in the parameters for optimum half-tone reproduction. The raster toner mark has pixels with toner and pixels without toner. If the optical density of the raster toner mark is below a lower limit, the bias voltage between the photoconductor and the developer station is increased so long as the current bias voltage is below an upper limit. The optical density may also be increased by increasing the ratio of toner mixed into the carrier particles. If the raster toner mark is above the target optical density, the bias voltage is decreased (if it is above a minimum level) and/or the ratio of toner to carrier particles is decreased. The combined effects of adjusting toner/carrier ratio (a slower process) with adjusting the bias voltage (a faster process) provides optimization of the half-tone printing.

What is claimed is: 
     
       1. A method for optimizing half-tone representation in electrophotographic printer or copier apparatuses, comprising the steps of: applying a raster toner mark on a surface.,   determining an optical density of said raster toner mark, determined integrally over a surface,   modifying at least one of a bias potential applied to a photoconductor of the electrophotographic printer or copier apparatus and a toner concentration,   said raster toner mark including repetitions of macropixels, said macropixels each being at least one dimension larger than a micropixel raster dimension, and being smaller than 0.5 mm, and said macropixels each including at least one micropixel that is not inked with toner, as well as at least one micropixel that is inked with toner.   
     
     
       2. A method according to claim 1, further comprising the step of: increasing the bias potential with respect to a current bias potential value if the optical density falls below a target value and is greater than a minimum value, and the current bias potential is below a maximum value.   
     
     
       3. A method according to claim 1, further comprising the steps of: maintaining the bias potential unmodified if the optical density corresponds to a target value.   
     
     
       4. A method according to claim 1, further comprising the step of: lowering the bias potential with respect to a current bias potential value, if the optical density exceeds a target value and is smaller than a maximum value, and the current bias potential is greater than a minimum value.   
     
     
       5. A method according to claim 1, further comprising the step of: increasing toner concentration if the optical density is smaller than the minimum value.   
     
     
       6. A method according to claim 5, further comprising the step of: lowering the bias potential during or shortly after a time of the increasing of the toner concentration.   
     
     
       7. A method according to claim 1, further comprising the step of: lowering the toner concentration if the optical density is greater than a maximum value.   
     
     
       8. A method according to claim 1, comprising the step of: providing additional comparison values between the minimum value of the bias potential and the maximum value of the bias potential.   
     
     
       9. A method for optimizing a half-tone representation in electrophotographic printer or copier apparatuses, comprising the steps of a) adjusting basic values,   b) before and during a print or copy process, producing a raster toner mark on a photoconductor, said raster toner mark includes repetitions of macropixels, each of said macropixels being at least one dimension larger than the micropixel raster dimension a and being smaller than 0.5 mm, and each of said macropixels having at least one micropixel that is not inked with toner and at least one micropixel that is inked with toner,   c) determining an optical density of the raster toner mark, measured integrally over a surface,   d) lowering a bias potential with respect to a current value of the bias potential if the optical value exceeds a target value and the bias potential is greater than a minimum value,   e) discharging, cleaning and recharging the photoconductor, and   f) repeating the steps b) to e).   
     
     
       10. A method according to claim 9, wherein said step d) also includes a substep of: lowering toner concentration with respect to a current value if the optical density is greater than a maximum value.   
     
     
       11. A method according to claim 9, further comprising the step of: increasing the bias potential if the optical density falls below a target value and is greater than a minimum value, and the bias potential is smaller than a maximum value.   
     
     
       12. A method according to claim 11, further comprising the step of: increasing toner concentration if the optical density is smaller than a minimum value.   
     
     
       13. A method according to claim 9, further comprising the step of: lowering toner concentration if the optical density is greater than a maximum value and the bias potential is less than or equal to a minimum value.   
     
     
       14. A method according to claim 9, further comprising the step of: increasing toner concentration if the optical density is less than a minimum value and the bias potential is greater than or equal to a maximum value.